Page 27: of Offshore Engineer Magazine (Nov/Dec 2013)

26 28

Geology & Geophysics safety) benefts. We are not bound by lim- itations on streamer tow spacing; so for example, in an exploration setting we can tow the cables further apart to effciently cover an area more quickly, reducing

Isometric sampling: turnaround time, whilst reconstructing the wavefeld to replicate closer-towed streamers. Wider spacing also mitigates

The next milestone in integrated 3D marine seismic the chance of streamer tangling. We can

OE: When was this system available to The compute power on-board the WG tow cables deeper in the water, where the clients? Vespucci—a vessel—makes it the fourth- ambient environment is quieter and they

CC: We completed feld testing in largest Schlumberger data processing are less affected by weather, but of course late 2011, close to our development center, worldwide. the tow depth also depends on the survey site, in the Norwegian North Sea. The There are two elements to onboard geophysical objectives.

IsoMetrix system was offcially launched processing: The quality uplift can be clearly seen in June 2012 at the EAGE conference 1. Take raw measurements through an in the standard seismic image volumes, in Copenhagen. Since then, we have initial online pre-conditioning step but it is necessary to look beyond these to completed seven projects in a wide range to remove noise associated with the 3D interpretational attributes and inver- of settings; including the North Sea, streamer construction and behavior in sion products to extract the full value. offshore United Kingdom and Norway; the water. For example, IsoMetrix volumes are

South Africa; the Barents showing great promise when

Sea; and a survey off partnered with ant-tracking to

Canada. map faults and fractures, and

SG

These surveys range with eXchroma which uses in size and objective, coloration to isolate geologic from exploration to information of other unconfor- reservoir characteriza- mities and lithology variations. tion for appraisal and Together, they allow for fresh development, including geological and interpretational a 4D qualifcation in the insights.

UK sector of the North

Sea, and cover a range OE: Is the technology of customers including unique?

independents, IOCs as CC: Yes. Although there is well as Schlumberger a range of broadband solu- multiclient projects. We tions, only IsoMetrix provides have a strong backlog of fully 3D deghosted broadband activity into 2014, and data in all dimensions that is will start a large program unique in the crossline gradi- for Woodside off north- ent measurement, allowing western Australia this accurate reconstruction of quarter. the pressure wavefeld. The

All surveys to date density of sensors along the

Broadband imaging in three dimensions for complex sand injectites using IsoMetrix technology. Photo: WesternGeco.

have been acquired using cable is important in character- the WG Vespucci, and we izing and removing the noise, plan to upgrade more vessels in 2014. 2. Production of a dense, isometrically to make best use of the accelerometer sampled up- and down going pressure information.

OE: How do you handle this much wavefeld on a 6.25-m x 6.25-m surface What it really comes down to is the data? grid. quality of images for explorationists

CC: The large amount of data is a major Additional fast-track processing runs and reservoir engineers. The fundamen- step-change for marine seismic acquisi- in parallel, and allows the client a quick tal benefts of the technology is that it tion. It’s not just the extra components look at the data. Then, we send the data provides fne isometric sampling to make we are measuring, which triples the ashore for further processing. Here we data more suitable for a wide variety amount collected. In order to characterize are able to leverage the experience of our of applications. The system provides and remove the noise, we must sample petro-technical experts from data condi- high-fdelity point-receiver seismic data, data more densely along the cable. The tioning, through imaging, inversion and that allows us to capture the seismic legacy is 3.125m spacing, but we sample interpretation to extract the maximum wavefeld on a 6.25-m x 6.25-m grid, at shorter intervals. To handle this value from the data. and yields the frst true 3D volume using enormous quantity of seismic data, we’ve towed streamers.

built an integrated acquisition and pro- OE: How does the client beneft? The earth is not simple, the subsur- cessing system that allows key elements CC: IsoMetrix technology offers quality, face is complex, and it is vital to get the of the processing to be done on board. effciency and operational (including full picture. oedigital.com November 2013 | OE 29 028_OE1113_GG_SLBIsometrix2.indd 29 10/27/13 4:24 PM